Use the chart below to determine which drive system you have.
Batteries left in a state of deep discharge for a year usually never come back to hold much of a charge, situation is worse yet if they are low on water... you can try a low amp (2-3) 12v charge on a single 8v... monitor the battery voltage and temp to make sure it does not rise above 11v and 95 degrees. Basically if the side of a battery gets warm to touch ~ stop charging. Never leave this process unattended. Check voltage every 30 minutes.
Good luck.
